what about problem in plant?

I agree with Ezzjaybruh - those roots are NOT looking good at all... and I've got to ask if you have any air stone in your bucket at all?! Are you leaving a good 1/2" to an inch of space between the water and the bottom of the netpot? Have you considered adding a root enhancer such as RapidStart? Botanicare's Hydroguard would also be something I would consider using... Also, try not to look at the roots much at all during a grow - they need to be kept in complete darkness as much as possible - hauling them out to look at them (unless you suspect a problem) creates the opportunity for pathogens and bacteria (the bad kind) to get in and do damage. If you suspect that, adding a healthy dose (3-6 tsps) of H2O2 will help kill the bad stuff... Are you measuring your EC or ppm? I don't see that information in your diary so am just curious... the plant looks like it needs more nutrition but that could be from a combination of the root issues and the low feed level... If you'd like to see what roots SHOULD look like, I took a video when I harvested a plant at Week 11 - it's the Creme de la Chem in my diaries... look in the harvest week. Good luck!

Huh? Roots are not in good shape from that pic